Chapter 17 Energy: Some Basics. History of Energy Crisis’ Greece & Rome – 2500 yrs ago –Energy source ---- WOOD local forests depleted - imported wood.

Chapter 17

Energy: Some Basics

History of Energy Crisis’• Greece & Rome – 2500 yrs ago

– Energy source ---- WOODlocal forests depleted - imported wood from as far as 1000 miles away

– Turned to solar energy• Built houses facing south

• Romans – used glass windows to increase effectiveness of solar heat

• Greenhouses were built to grow veg. in the winter

• Illegal to build a structure that shaded another

TURNED TOWARD SUSTAINABILITY

U. S. Energy History

• Use of wood in US peaked in 1880’s (coal was widespread and also needed to be burned)

• Coal use decreased in 1920’s when oil and natural gas became available.

Energy Basics

Energy: the ability to do work

Potential Energy: energy that is stored (or due to position)

Kinetic Energy: energy of motion

- All energy is either potential or kinetic

1st Law of Thermodynamics

• Energy is neither created nor destroyed, it is transformed

• Total energy in a system is ALWAYS conserved

• Types of energy: KE, PE, thermal, chemical, electrical, electrochemical, electromagnetic (light), sound and nuclear.

Example – Tire Swing

• PE transforms to KE transforms to Heat Energy

• The QUALITY of energy has also changed

• The availability of the energy to “do work” has changed.– Increase energy quality = easily does work

• (ie- oil, n.gas, coal)

– Decrease energy quality = more difficult to do work

• ( heat)

2nd Law of Thermodynamics

• Energy always tends to transform from a high quality energy to a lower quality energy

– ** When you USE energy, you lower its quality

POWER

• Energy – the ability to do work (W = Fd)

• Power – the rate at which work is done– Unit for power = Watt– Kilo (1000), Mega (mill.), Giga ( bill.)– A nuclear power plant produces electricity at a

rate of 1000 MW or 1GW

• Power = work/time or energy/time– Therefore energy = power x time– Unit for energy is Watt-hour (Wh) – electricity

is sold in KWh (kilowatt-hours)

• Energy used annually

• (KWh/yr) = Power rating X time used in a year– (convert Watts to KW)

– READ “A Closer Look 17.1” on page 351 in text – interpret Table 17.2

Energy Efficiency• First Law Efficiency

– Ratio of amount of energy delivered to amount of energy supplied

• Ex. A natural gas burning furnace delivers 1 Unit of heat to the house for every 1.5 Units of energy extracted from the burning of the fuel.

• 1/1.5 = .67 = 67% efficiency

• Second Law Efficiency– How well matched the energy end use is with

the quality of the energy source• Compare minimum energy necessary to heat a home with the energy

actually used

• Ex. You could use an acetylene torch to light a candle or a match. The match is more efficient !!!

Energy Sources & Consumption• Energy consumption is directly related to a

countries “standard of living”– ^ standard of living = ^ energy consumption– US (5% of the world’s pop.) used 25% of all

energy consumed in the world– 90% of energy consumed in US is fossil fuels– Energy consumption has risen steadily form

1950 to today – with a dip in the 1980’s when energy conservation became popular

Energy Conservation, Increased Efficiency and Cogeneration

Conservation: getting by with less demand for energy

Energy Efficiency: designing equipment to yield more energy output from a given amount of input energy

Cogeneration: a number of processes designed to capture and use waste heat rather than simply to release it into the atmosphere

Ex. N.Gas powerplant – produces electricity in two ways:

1- burning gas (gas cycle)

2- heat energy given off by the gas cycle is used to create steam which produces electricity (steam cycle)

Energy Policy• Hard Path vs. Soft Path

– Hard Path: finding greater amounts of fossil fuels and building larger power plants

– Soft Path: involves energy alternatives that emphasize energy quality and flexibility

• Integrated, Sustainable Energy Management– Integrated Energy Management: no single energy

source can provide all the energy required by the world– Sustainable Energy Management: provides reliable

sources of energy without causing serious harm, all while ensuring that future generation inherit a fair share of Earth’s resources

Energy Policy Act of 2005• Recommends using coal & n.gas with the

objective of reducing our reliance on energy from foreign countries

• Promotes nuclear power• Encourages alternative energy sources• Promotes conservation methods – increase

efficiency standards in federal bldgs & household product.

• Promotes research & development – improve coal powerplant emissions

• Keep up energy infrastructure – dependable electric grids